The objective of this research is to determine what effect perinatal (in utero or through lactation) exposure to foreign compounds has on the development of basal and inducible mixed function oxidase (MFO) activities later in life. Rats will be employed. Perinatal exposure will be provided by classical enzyme inducers such as phenobarbital and beta-naphthoflavone administered to the dam. Subsequent MFO activities will be monitored from birth through adulthood. The relevance of these activities for the disposition of two carcinogens, aflatoxin B1 and 3-methylcholanthrene, will be determined by measurement of the proportion of the doses which covalently bind to tissue macromolecules. This research is designed to determine whether exposure during the embryological development period presets the level of MFO enzyme activity and, perhaps, carcinogenic risk observed after birth.